LocalSend up to 1.16.x prepare-upload path traversal

Summaryinfo

A vulnerability marked as critical has been reported in LocalSend up to 1.16.x. This issue affects some unknown processing of the file /api/localsend/v2/prepare-upload. This manipulation causes path traversal. The identification of this vulnerability is CVE-2025-27142. The attack needs to be done within the local network. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in LocalSend up to 1.16.x. Affected by this vulnerability is an unknown code of the file /api/localsend/v2/prepare-upload. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

LocalSend is a free, open-source app that allows users to securely share files and messages with nearby devices over their local network without needing an internet connection. Prior to version 1.17.0, due to the missing sanitization of the path in the `POST /api/localsend/v2/prepare-upload` and the `POST /api/localsend/v2/upload` endpoint, a malicious file transfer request can write files to the arbitrary location on the system, resulting in the remote command execution. A malicious file transfer request sent by nearby devices can write files into an arbitrary directory. This usually allows command execution via the startup folder on Windows or Bash-related files on Linux. If the user enables the `Quick Save` feature, it will silently write files without explicit user interaction. Version 1.17.0 fixes this issue.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2025-27142 since 02/19/2025. The exploitation appears to be easy. The attack needs to be initiated within the local network. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1006 according to MITRE ATT&CK.

Upgrading to version 1.17.0 eliminates this vulnerability. Applying the patch e8635204ec782ded45bc7d698deb60f3c4105687 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• LocalSend

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16

License

• open-source

Website

• Product: https://github.com/localsend/localsend/

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